Axial piston pump or motor



Jan. 19, 1965 o. THOMA 3,166,016

AXIAL PISTON PUMP 0R MOTOR Filed Feb. 26, 1964 2 Sheets-Sheet 1 I/VVENWR oswnLb 77: 007/? 'Jan. 19-, 1965 o. THOMA 3,166,016

' AXIAL PISTON PUMP 0R MOTOR I Filed Feb. 26, 1964 2 Sheets-Sheet '2 FIG. 2 66 INVENTOR Oawnlb 71mm 3 1d g M ATTORA/E Ys 3,166,016 AmAL PISTON PUMP R MOTOR Oswald Thoma, Charlton Kings, Gloucester, England,

assignor to Unipat A.G., Glarus, Switzerland, a com- This invention relates to axial piston pumps or motors.

In accordance with the presentinvention a pump or motor comprises a rotary cylinder block having cylinder bores arranged parallel or slightly inclined to the block rotation axis, pistons in the bores extending one from each end of the block, two cam plates located one at each end ofthe cylinder block, each of which has a surface inclined to the block rotation axis against which the pistons are arranged to react and valve means controlling fluid entering to and fluid delivery from the cylinders, one cam plate being mounted for angular adjustment relative to the other cam plate about the block rotation axis for adjustment of the volumetric displacement per revolution of the block.

Preferably one of the cam plates is fixedly mounted in a support carrying the two cam plates, the other cam plate'being angularly adjustable within the support.

The valve may comprise a plurality of cylinder ports in a valve surface of the cylinder block and inlet and delivery ports in the co-operating valve surface of a valve member, the valve member being connected to at least one swash plate by gearing such that rotation adjustment of the valve member about the block axis is one half the relative angular adjustment between the swash plates. j

Two embodiments of the invention will now be described with reference to the accompanying drawings in which: 1

. FIG, 1 is a cross-sectional view of an axial piston pump according to the invention,

FIG. 2 is a view similar to FIG. 1 with another embodiment of the' invention.

The embodiments are intended for use as variable displacement pumps but because they include valve means positively operated during rotation of the pump they could equally well be used as motors. i

Reference is first made to FIG. 1. The housing of the pump comprises a cylindrical casing l having two end plates 2 and 3. 'A rotary cylinder block 4 is mounted within the housing and includes a plurality of'cylinder bores 5 disposed parallel to the block rotation axis and equally spaced around the axis.- Within each cylinder bore 5 a pair of pistons 6 and 7 are slidably mounted, and a spring .8 acting between the pistons to urge them outwardly. The outer ends of the pistons each carry a slipper respectively 9 and 11 secured to the associated'piston by means of a ball joint respectively 12 and 13. The slip pers 9 engage on an inclined surface 14 which forms the inner surface of the end plate 3. This surface is inclined to the rotation axisof the cylinder block. Thus the end plate 3 forms a swash plate. The slippers 11 engage on the inclined surface 15 of a swash plate 16 mounted in the housing adjacent to the end plate 2.- The swashplate 16 is capable of angular movement within the housing by virtue of bearing inserts 17 and 18 which absorb radial and axial loads respectively exerted on the swash plate.

A central hole within the end plate 3 accommodates a roller bearing 19 which locates radially the pump drive shaft 21. The drive shaft 21 is integrally formed with the block 4. A shoulder 22 located at the position where the drive shaft joins theblock locates a ball axial thrust bearing 23 which engages against the end plate 3 to resist :1 United States. Patent 0 in phase by degrees the axial loads exerted on the block 4. At the opposite end of the block 4 there is a central recess 24 haying a hearing insert 25 into which fits an annular projection 26 from the swash plate 16. Engagement of the projection 26 on the bearing insert 25 locates radially the end'of the cylinder block 4 oppositeto the drive shaft 21.

The central bore 27 of the annular projection 26 extends completely through the swash plate 16 and at its outer end is enlarged to receive a ball bearing 28. Within the ball bearing 28 a valve support member 29 is rotatably mounted which extends. from the recess 24 through the swash plate 16 and the end plate 2 to the exterior of the pump. Exteriorly of the pump the supportmember 29 is fitted with a rotary joint 31. Fixed hydraulic supply and return pipes 32 and 33 extend from the rotary joint 31 and within the rotary joint hydraulic connections are made from the pipes 32 and 33 to a pair of passages 34 and 35 within the support 29. In the central bore 27 of swash plate 16a bearing insert 36 locates the inner end of the valve support 29 for rotation.

The inner end of the support 29 includes a recess 37 which houses a valve plate 38. The recess 24 includes a valve surface formed on the block which is fiat and perpendicularly disposed. to the rotation axis of the block. Against this surface a flat valve surface 41 0f the valve plate 38 engages. From each cylinder 5 a passage 42 extends through the cylinder block to terminate in a. port 43 in the valve surface 39. In the valve plate 38 a pair of ports 44 and 45 are located in hydraulic connection with passages 34 and 35 in the support. The ports 44 and 45 are of conventional kidney shape and during rotation of the cylinder block the cylinder ports 43 alternately co-operate with the kidney ports 44 and 45. g The valve plate 38 is supported against rotation on the support 29 by means of 'a pair of hollow sleeves 46 and 47 which at the same time effect hydraulic connection'between passages 34, 35 and ports' 44, 45; The sleeves 46 and 47 are carried by bores both in the support and the valve plate so that hydraulic pressure therein may act on the valve plate 38 to urge it axially so that its surface 41 engages the valve surface 39. The axial thrust exerted by the valve plate 38 on the cylinder block is resisted by the axial thrust bearing 23 acting between the cylinder block and the end plate 3. The corresponding axial reaction in the opposite direction is exerted on the support 29 and this is reacted through the bearing'ZS, the cam plate 16 and the bearing insert 18ontothe end plate 2.

The cam plate 16 has a gear wheel 48 secured thereto which extends through an opening 49 in the end plate 2. The valve support 29 also has a gear wheel 51 secured thereto which lies adjacent to the gear 48. The gear 51 is of larger diameter than the gear 48.

A displacement control shaft 52 is rotatably mounted in a bearing 53 in the end plate 2 and has secured thereto a pairof gear Wheels 54 and 55 which are in mesh respectively with the gear wheels 48 and 51. The gear ratio between the gears 54 and 48 is arranged to betwice the gear ratio between the gears 55 and 51 so that for any. 7

angular movement of the shaft 52 the movements of the gears 48 and 51 are in the ratio 2:1.

In operation of the pump illustrated, rotational move ment applied to the drive shaft 21 willrotate the block 4 which in turn will cause the pistons to reciprocate -by virtue of the engagement'of their slippers with twoinclined surfaces-14 and 15. The relative phasing'between the reciprocations of the two pistons 6 and'7 in each cylinder will effectively determine the displacement of the cylinder per revolution. For example if the reciprocatory motions of the two pistons in one cylinder are displaced be at a maximum.

V Patented Jan. 19, 1965 volumetric displacement will 7 6 and 7 are completely in phase there will be no displace- 'ment since the volume between the pistons will not alter.

At intermediate phase positions between and, 180 degrees the volumetric displacements: from each cylinder will lie in between zero and the maximum. The phase angle between reciprocations of the pistons 6 and 7 inany cylinder is approximately equal to the angular relation of the cam plates 3 and 160m to the other about the rotation axisof the cylinder barrel. In FIG. 1 only the one cam plate 16 is rotatable .and it occupies a position in 7 14 and lS will be parallel and the reciprocation of the pistons during cylinder block rotation will be in exact phase agreement with the result that there will be no displacement from the cylinders. In this condition it can be said that the angular displacementof the cam plate 16 from the end plate 3 is zero about the axis of thecylinder block. Since the cam plate 16.may be rotated smoothly to occupy any angle between 0 and 180 degrees relative tothe end plate 3 it will beseen that'displacement from the cylinders may be adjusted to any displacement from zero to the maximum.

handle 64and 66 respectively, which handles extend I through slots 65 and-67 in end cover 61 and end plate 2. The handles and are interconnected by suitable In considering the phasing of the reciprocatory movement of the pistons no mention has yet been made of the g;

. operation of the valve. The consideration of the displacement from the cylinders has been based on theas sumption that there 'is efiicient valve operation which will auto-' matically connect each cylinder during increase in its volume to an input passage and during decrease in its volume to a delivery passage. This result could be obtained without dilficulty by using a pair of simple nonreturn valves connecting each cylinderto the inletand delivery passages. Such non-return valves would clearly? limit the illustrated device to use'only'as a pump. 'In the described embodiment a rotary valve arrangement has been described which'positively connects the cylinders during rotation to input and deliverypassagesin such a Way that duringincrease in volume in a cylinder it is connected to the input passage and during reduction in 'volume in a cylinder it is connected'to the delivery passage.

In theposition of the cam plate 16 shown in the'drawing i.e. at 180'degrees displacement from the end plate 3, the kidney ports 44 and are so arranged that one is in connection with all cylinders inwhich the volume is increasing, and the other is in connection with all cylinders in which the volume is decreasing. The gears 48, 51, 54, 55, which give to the valve" support 29 angular movement only one half of that given to the camplate'16, ensure approximately that for any angular positionof the cam f plate 16 between 0 to 180 degrees that one of the kidneyports is always in connection with cylinders whose volume is reducing and the other kidney port is always in connection with cylinders whose volume is increasing.

If this relation between the kidney ports 44 and 45 and 1' the cylinders is not observed then the condition might arise that thechange over of the connection of a cylinder port 43 from one kidney port 44 to the other'kidney port 45 would occur at a position where .the volume of -the cylindner is changing at a substantial rate. If the change over occursduring decrease in volume of a cylinder the momentary blockage at the. change over would cause an excessively highpressure pulse to be generated in the cylinder'which could damage the pump; vAlternatively if such change over occurs during increase in volume of a cylinder cavitation, could occur within that cylinder. However,,the embodiment shown in the drawing ensures ap- I isprovided capable of axial movement under hydraulic pressure to efiect sealing engagement with the valve surface 39 of the cylinder block it will be appreciated that other forms of rotary valves can be used withinthe scope of the present invention, for example a pintle valve could be used in substitution 'for the plate valve illustrated. Further it will be appreciated that if the device is for use as a pump only it is possible to employnon return valves as previously described instead of a' rotary valve.

In the embodiment of FIG. lthe cylindrical casing 1 forms a support to which end platev 3 is fixed whilst the cam plate 16 is relatively movable. However, it is within the scope of .the invention that both the plates could be 7 simultaneously adjustable relatively to the support and i such an embodiment is shown in FIG. 2 in which also the end plate 3' is mounted in the casing 1 for angular adjustment about the block rotation axis by means of axial thrust bearing and radial bearing 62. Axial bearing 60 cooperates with an end cover 61 fixed tothe casing 1. 20

The angular adjustment of end plate 3' is equal but opposite to the angular adjustment 'of cam plate 16. For such angular adjustment eachplate 3' and 16 carries a gearing (not shown) to ensure simultaneous and equal but opposite adjustment of the plates. In FIG. 2 the plates 3'.

and 16 occupy the same position relative to each other as. in FIG. I and consequently the displacement from the cylinders 5 is at a'maximum. If the plates 3' and 16 are rotated by 90 degrees in opposite directions from this position the surfaces 14 and 15 will be parallel and the displacement from the cylinders will be zero. The valve support member 29' is fixed against rotation relative to the casing 1 and screws 68.

In theillustrated examples cylinder. bores are shown What Ilclaim is:

7 Whilst in. the described construction a valve plate 38 1. An axial piston apparatus comprising a stationary support structure having first and second annular end i plates, a rotaryicylinder block having a first and second end portion, means" for rotationally mounting said block within said support structure, said block having aplurality 1 of cylinder bores'formed' therein and extending in a generally axial direction, a pair of pistons in each of'said cylinder bores, said first and second annular endplates having first and second cam means disposed thereon, each oiwhich has a cam surfaceinclined to the block rotation axis,.said pair of pistons in each of said bores being biased into sliding engagement with the cam surface of said first and second cam means,.valve means for controlling fluid entry to and fluid delivery from. each of said bores, means supporting said valve means so that the latter means extends through the central opening in said second annular end plate and said second cam means so as to abut the second end portion of said block, passage means in said vblock for connecting said valve means to said bores, and means engagingrsaid second cam means and said valve means for angularly adjusting 'both of said latter mentioned means about the rotational axis of said block such that the angular adjustment of said valve means is half the angular adjustment of said second cam means for adjustment of the volumetric displacement offluid per revolution of said block. 7

The apparatus as. defined by claim 1 wherein said is secured to the endplate 2 by means of adjustment means comprises a shaft journalled into said second annular end plate for rotary movement and a pair of gears fixed on said shaft, 21 first gear connected to said second cam means, a second gear connected to said valve means, said shaft gears meshing Withsaid first and second gears respectively.

3. The apparatus of claim 1 in which said means to support said valve means comprises an annular projection formed on said second cam means, the internal surface of said annular projection having means thereon for supporting said valve means for angular rotation Within said projecting portion of said second cam means. I

4. The apparatus of claim 1 wherein said means'to mount said block within said support structure includes in part a drive shaft which is connected to said first end portion of said block and journalled for rotation in said first annular end plate.

5. The apparatus of claim 4 wherein said means to mount said block Within said support structure further includes an annular cut out portion in said second end portion of said block, an annular projecting portion formed on said second-cam means and directed toward said annular cut out portion, said projection being received within said out out portion to support the second end portion of said block for rotation. V V.

6. An axial piston apparatus comprising a supporting structure having first and second annular end plates connected thereto, a rotary cylinder block having a first and second end portion with an annular cut out portion in said second end, a plurality of cylinder bores formed in said block and extending in a generally axial direction, a pair of pistons in each of said cylinder bores, said first and second annular end plates having first and second cam means adjustably disposed thereon with each of said cam means having a cam surfaceinclined to to and fluid delivery from each of said bores, said second cam means having an annular projection, said projection.

directed toward and received within the annular cut out portion in said second end portion of said block, said valve means received within said annular projection and connected to said second annular end plate so that the valve means abuts the second end portion of said block, means insaid block for connecting said valve to said bores, means connected to said first and second cam means for angularly adjusting said cams in equal and opposite directions, and a drive shaft connected to said first end portion of said block and journalled to said first annular end plate, .said drive'shaft and said annular projecting FOREIGN PATENTS,

589,670 6/47 Great Britain.

LAURENCE V.'EFNER, Primary Examiner.

the block rotation t Y axis, said pair of pistons in each of said bores being biased into engagement with the cam surface of said first and second cam means, valve means for controlling fluid entry 7 

1. AN AXIAL PISTON APPARATUS COMPRISING A STATIONARY SUPPORT STRUCTURE HAVING FIRST AND SECOND ANNULAR END PLATES, A ROTARY CYLINDER BLOCK HAVING A FIRST AND SECOND END PORTION, MEANS FOR ROTATIONALLY MOUNTING SAID BLOCK WITHIN SAID SUPPORT STRUCTURE, SAID BLOCK HAVING A PLURALITY OF CYLINDER BORES FORMED THEREIN AND EXTENDING IN A GENERALLY AXIAL DIRECTION, A PAIR OF PISTONS IN EACH OF SAID CYLINDER BORES, SAID FIRST AND SECOND ANNULAR END PLATES HAVING FIRST AND SECOND CAM MEANS DISPOSED THEREON, EACH OF WHICH HAS A CAM SURFACE INCLINED TO THE BLOCK ROTATION AXIS, SAID PAIR OF PISTONS IN EACH OF SAID BORES BEING BIASED INTO SLIDING ENGAGEMENT WITH THE CAM SURFACE OF SAID FIRST AND SECOND CAM MEANS, VALVE MEANS FOR CONTROLLING FLUID ENTRY TO AND FLUID DELIVERY FROM EACH OF SAID BOREA, MEANS SUPPORTING SAID VALVE MEANS SO THAT THE LATTER MEANS EXTENDS THROUGH THE CENTRAL OPENING IN SAID SECOND ANNULAR END PLATE AND SAID SECOND CAM MEANS SO AS TO ABUT THE SECOND END PORTION OF SAID BLOCK, PASSAGE MEANS IN SAID BLOCK FOR CONNECTING SAID VALVE MEANS TO SAID BORES, AND MEANS ENGAGING SAID SECOND CAM MEANS AND SAID VALVE MEANS FOR ANGULARLY ADJUSTING BOTH OF SAID LATTER MENTIONED MEANS ABOUT THE ROTATIONAL AXIS OF SAID BLOCK SUCH THAT THE ANGULAR ADJUSTMENT OF SAID VALVE MEANS IS HALF THE ANGULR ADJUSTMENT OF SAID SECOND CAM MEANS FOR ADJUSTMENT OF THE VOLUMETRIC DISPLACEMENT OF FLUID PER REVOLUTION OF SAID BLOCK. 